Method of making a sealed junction between aircraft parts

ABSTRACT

In the method of making a sealed junction between elongate aircraft parts that extend locally in main directions that are not mutually parallel, the following steps are performed: assembling a plurality of portions of a mold on the parts; and injecting a sealing material into the mold.

The invention relates to structural portions of aircraft, such asfuselages.

It is known to provide a structural partition inside the fuselage of anairplane in order to separate the inside volume into two gas- orliquid-tight zones. For example, one of the zones defined by thepartition may be pressurized, unlike the other zone, or one of the zonesmay be used as a fuel tank. The junction between the partition and thewall of the fuselage is made at an angle that is locally perpendicularto the wall and to the parts of the primary structure of the airplane,which structure comprises frames, stiffeners, stringers, beams, etc.

Such a partition may be installed permanently when the airplane isfabricated. However it may be desirable to install such a partition as aretrofit, i.e. in an airplane that was not originally designed toreceive it. This applies in particular for an airplane that has alreadyflown.

Unfortunately, putting such a partition into place raises variousproblems. Since it is a structural partition, it must be capable ofwithstanding required levels of force. For this purpose, it is known tofasten the partition to the primary structure by means of fishplatesextending on either side of the partition and requiring at least twoparts and a plurality of structural fastenings. It is preferable tofasten the partition to the fuselage without cutting into the parts ofthe primary structure of the airplane so as to avoid endangering itsmechanical properties. However, when it is also desired to save weight,such an arrangement is found to be too heavy or to be critical in termsof fatigue. Thus, in certain circumstances, sealing is provided byputting putty into place that is sandwiched between the parts. Thatsolution requires a large number of small pieces of thin sheet metal tobe added, which pieces are complex to install.

An object of the invention is to provide a sealed junction betweenparts, in particular structural parts, e.g. while retrofitting theaircraft.

To this end, the invention provides a method of making a sealed junctionbetween elongate aircraft parts that extend locally in main directionsthat are not mutually parallel, wherein the following steps areperformed:

-   -   assembling a plurality of portions of a mold on the parts; and    -   injecting a sealing material into the mold.

Sealing is thus achieved by means of a sealed block that is molded insitu on the part. Where necessary, this sealing can be made to becompatible with a pressure differential between opposite sides of theblock. The method is easily implemented on an existing airplane, e.g. onan airplane that is being converted with major structural modifications.It is inexpensive and easy to perform. It does not require the additionof parts that remain permanently in place, nor does it require theinstallation of fastenings other than those needed for keeping the moldtemporarily in place. The block that is made is of the appropriatevolume. The method may be implemented repetitively while keeping controlover the weight of material that is installed in this way. If necessary,the sealed junction may be removed, and then remade should that benecessary, without inflicting any structural damage. This advantage isparticularly important when it is necessary to repair or to visuallyinspect the zone in question within the aircraft. The method may beimplemented by using a sealing material that is sufficiently flexible toaccommodate the movements between the structural parts while theaircraft is in use. The invention is applicable to a structural portionof an aircraft such as a fuselage, a wing, or a tail.

Preferably, the parts form a frame and a stringer of a fuselage.

This arrangement is thus particularly useful for sealing a partitionbetween a front zone and a rear zone of an inside volume of thefuselage.

Preferably, prior to injection, at least one block of sealing materialis installed in the mold, in particular facing a face of one of theparts oriented in a direction opposite to the other part.

This provision makes it easier to install the sealed junction, inparticular when it is to represent a volume that is relatively large, orindeed when certain zones may be difficult to fill in with the sealingmaterial that is initially in a liquid or pasty state.

Preferably, at least two of the mold portions present respective notchesfor receiving one of the parts.

Preferably, at least two mold portions are clamped one towards the otherby using clamping means such as self-blocking fasteners, and then afterinjection the clamping means are cut off level with a face of thesealing material.

Thus, a fraction of the clamping means remains permanently in thesealing block and is thus sacrificed.

Advantageously, at least one of the clamping means bears directlyagainst one of the parts, between said parts.

Preferably, at least one of the mold portions is inserted in a housingfacing a face of one of the parts that is oriented in a directionopposite to the other part.

Preferably, the or each inserted mold portion is made of a cellulardeformable material.

Preferably, a sealed junction is made using the same mold portions onother parts of the same aircraft presenting shapes and/or dimensionsthat are different from the shapes and/or dimensions of the parts.

Thus, the same mold portions are used at different locations of theaircraft in spite of differences of configuration in the parts that areto receive the sealed junction.

The invention also provides an aircraft that comprises elongate partsthat extend locally in main directions that are not mutually parallel,and a molded block forming a sealed junction between the parts.

The aircraft preferably includes a structural portion such as afuselage, a wing, or a tail, which structural portion comprises:

-   -   a wall separating the inside from the outside of the structural        portion and comprising fractions that define between them an        inside volume of the structural portion; and    -   a structural partition separating zones of the volume, e.g. a        front zone and a rear zone from each other, the partition        comprising a flexible diaphragm suitable for deforming and        supports supporting the diaphragm in discontinuous manner;    -   the block providing a sealed junction between the partition and        the remainder of the structural portion.

The diaphragm thus serves to adapt the dimensions of the partition tothe actual dimensions of the already-made structural portion and to thedeformations to which it is subjected while the aircraft is in use.Furthermore, the supports enable the partition to take up the necessarystructural forces and to transmit them to the structural portion. Thepartition may be installed in an existing aircraft in a short period oftime, and thus without keeping the aircraft grounded for a long time.Installation can be performed in a manner that is relatively simple andinexpensive. Although the partition of the invention is particularlyappropriate for retrofitting, i.e. for said partition being put intoplace inside an already-existing aircraft, or at least in a structuralportion that has already been made, the invention is also usable for usewith original equipment, i.e. for fastening such a partition duringinitial construction of the aircraft.

Other characteristics and advantages of the invention appear furtherfrom the following description of an embodiment given by way ofnon-limiting example and with reference to the accompanying drawings, inwhich:

FIG. 1 is a longitudinal vertical axial section view of an aircraft ofthe invention showing the principle on which the partition isconfigured;

FIG. 2 is a rear view of the FIG. 1 fuselage showing the stationaryelements supporting the partition;

FIG. 3 is a view analogous to FIG. 2 showing the center portion of thepartition that is to be fastened to the stationary elements of FIG. 2;

FIG. 4 is a view analogous to FIG. 2 showing the principle on which thediaphragm supports are arranged;

FIG. 5 is a detail view analogous to FIG. 4;

FIG. 6 is a section view on plane VI-VI of the FIG. 3 partition;

FIG. 7 is a larger-scale view of detail D of FIG. 1 showing how the topportion of the partition is fastened;

FIG. 8 is a view analogous to FIG. 7 showing how the top portion of thesealing diaphragm is fastened and showing how it is deformed;

FIG. 9 is a larger-scale view of detail E of FIG. 1 showing how thebottom portion of the diaphragm is fastened;

FIG. 10 is a section view on plane X-X of the FIG. 5 partition showinghow its side portion is fastened;

FIGS. 11 and 12 are larger-scale views of details F and G of FIGS. 6 and11 respectively;

FIG. 13 is a perspective view of one of the segments of the FIG. 11diaphragm;

FIG. 14 is a section view showing how the bottom portion of the wall issealed;

FIG. 15 shows how the partition is sealed at other locations;

FIGS. 16, 17, and 18 are section views showing the use of a mold formaking a sealing block for the partition of the preceding figures,respectively on planes XVI-XVI, XVII-XVII, and XVIII-XVIII of FIGS. 17and 16;

FIGS. 19 and 20 are section views showing how mold portions are sealed,the section of FIG. 19 being on plane XIX-XIX of FIG. 17;

FIG. 21 is a section view on plane XXI-XXI of the arrangement of FIG.17;

FIG. 22 is a view analogous to FIG. 11 showing the forces exerted by thediaphragm 60 on one of the beams of the partition when the partition issuch that these forces are not balanced;

FIG. 23 is a view analogous to FIG. 22 in which the partition is suchthat the forces are balanced; and

FIG. 24 is another larger-scale view of detail G of FIG. 11.

The aircraft shown in FIG. 1 is an aerodyne, and more specifically anairplane 2. It comprises a fuselage 4 of generally elongate cylindricalshape having the horizontal axis 6 as its main axis. The front of thefuselage has a cockpit 8. The airplane is provided with wings (notshown), landing gear, a portion 10 of which is visible in FIG. 1, andengines 12.

Below, reference is made to an X, Y, Z rectangular frame of reference inwhich the X and Y directions are horizontal and mutually perpendicular,the X direction being parallel to the axis 6, and the Z direction isvertical.

It is assumed here that fabrication of the aircraft 2 has beencompleted, or indeed that the aircraft has already flown. The idea is toinstall a removable sealed structural partition during a retrofit stage.This partition is designed to be sealed so as to be air-tight againstthe cabin pressure that is to exist on one side only of the partition,specifically in front of it. It is also desirable to ensure that thepartition can be installed quickly and also removed quickly, should thatbe necessary, i.e. within a few hours.

The fuselage has frames 14 of circular shape, each extending generallyin a plane that is perpendicular to the axis 6 and carrying the skin 28of the fuselage. The skin is reinforced by horizontal stringers 116 inthe form of section members that are also fastened to the frames. Theframes are arranged in mutually parallel planes that follow one anotheralong the axis 6. It is assumed here that the partition is installed soas to extend generally in a plane that is perpendicular to the axis 6,in the vicinity of the frame numbered 30 in the succession of framesthat starts at the nose of the aircraft.

A rigid subassembly 22 is provided to support the partition 20, thesubassembly being rigidly fastened to the fuselage 4 and specificallybeing permanently fastened thereto. It extends at the periphery of thepartition. It comprises the left and right lateral segments of the frame14 together with top and bottom plane panels 24 and 26. The panels arefastened directly to the skin 28. The top panel 24 extends continuouslyfrom the fuselage skin 28 to the height of a ceiling of a cabin of theairplane. The bottom panel 26 extends continuously from the skin 28 tothe height of the floor of the cabin. These panels are fastened to themain structure of the airplane. Each of them is self-stiffened, andspecifically each is provided with vertical rectilinear elongatestiffeners 30 that are parallel and spaced apart from one another. Thetop and bottom panels 24 and 26 may present openings 110 for allowingvarious systems to pass through them, such as ducts for air and liquid,e.g. water, electrical and computer cables, etc.

With reference to FIG. 3, the partition 20 comprises a subassembly 32that is fastened to the subassembly 22 by means enabling it to beremoved easily and quickly. The subassembly comprises a non-rigidframework comprising rigid portions 34 and deformable flexible zones 36.In the present example that is shown in detail in FIG. 5, there are fiverigid portions 34 and five deformable flexible zones 36.

Specifically, the rigid portions and the flexible zones follow oneanother in alternation from one side of the fuselage to the other, herebeginning on the left with a rigid portion 34, and as represented by theletters “R” and “S” (for “supple”) in FIG. 4. Each portion or each zoneextends over the full height of the subassembly 32. Those that are inthe middle zone of the subassembly are generally rectangular in shape.There are six of them in this example as can be seen in FIGS. 3, 4, and5, and they extend from the top panel 24 to the bottom panel 26 to whicheach of them is fastened individually.

In this example, each of the rigid or support portions 34 comprises twovertical rectilinear beams 40 that are spaced apart from each other,e.g. at a spacing of 500 millimeters (mm). The beams are preferablysituated in register with longitudinal rails of the floor of theaircraft. Each rigid portion has stabilizers in the form of intercostalties 42 rigidly interconnecting the two beams. The stabilizers arefastened to the beams at a distance from the ends thereof and they areregularly spaced apart vertically along the beams, co-operatingtherewith to form a ladder configuration. The stabilizers 42 as fastenedin this way to the beams make each portion 34 rigid.

With reference to FIGS. 11 and 12, each beam 40 is formed by a sectionmember of generally H-shaped section. The rear flange plate 44 of thesection member is plane in shape, while the front flange plate, as shownin detail in FIG. 12, is shown as being generally an upside-down V-shapesuch that the two flanges 48 of the flange plate are rearwardlyinclined. Each flange thus presents a vertical plane front face 50 thatis inclined towards one side of the fuselage, e.g. forming an angle ofabout 30° relative to the transverse direction Y.

Each stabilizer 42 is generally plane in shape and extends in ahorizontal plane. It may present holes 52 in order to reduce its weight.In this example its rear edge is rectilinear, while its front edge 54presents a concave curved shape, e.g. a circularly arcuate shape, suchthat the middle portion of this edge is closer to the rear edge than areits end portions. The stabilizer 42 is fastened to the ribs 56 of theassociated beams 40. The edge 54 is also set back from the flanges 48and thus from the front faces 50 thereof.

At least one of the rigid portions 34 may be arranged to receive a door74, as shown in FIG. 4, or a passage of some other type enablingequipment or crew to pass through the partition. The door may beprovided with a frame having a Z-shaped profile including a sealinggasket. The door may comprise a self-stiffened skin, two horizontalfittings supporting hinges and door stops, an operating and lockingmechanism, and a safety porthole.

Each rigid portion 34 carries a segment of deformable flexible diaphragm60 that is fastened to the beam 40 so as to be capable of moving anddeforming. Specifically this is a layer of non-metallic material such asan aramid resin in the form of fibers, e.g. a poly-para-phenyleneterephthalamide as sold under the name Kevlar. This resin is embedded ina layer of silicone by an injection method, such that the diaphragm 60is reinforced and is capable of withstanding a cabin pressuredifferential of the type to which an airplane flying at stratosphericaltitude may be subjected.

The diaphragm 60, shown in particular in FIG. 13, has mutually parallelvertical rectilinear side edges 62, whereby it is fastened to the faces50 of two corresponding beams by being sandwiched between the flange 48and a strap 64. The strap is fastened to the flange, e.g. by means ofbolts 66, washers, and captive nuts 68 located at the rear portion ofthe flange.

As shown in particular in FIG. 11, the diaphragm segment 60 is fastenedto the beams so that on going from one beam to another, it has a shapethat is not plane, specifically it has a rounded shape of cylindricalhorizontal section. The diaphragm thus extends along the front edge 54of the stabilizer 42, while remaining at a distance therefrom all alongits length. The radius of curvature of the diaphragm may for example beless than or equal to 800 mm. The diaphragm is mounted so as to becapable of reversing its curvature, i.e. inverting it, such that itscenter of curvature is no longer in front of the partition but is behindit, as shown by dashed line 60′. This reversal may occur for example inthe event of the depressurization of the cabin.

As shown in FIG. 13, the top and bottom end portions 70 of the diaphragmsegment have a configuration that is rounded in two mutuallyperpendicular directions, specifically a spherical configuration. Inthis example, the top and bottom edges 72 of the diaphragm arerectilinear and horizontal.

The flexible zones 36 of the partition 20 are formed solely by onesegment of reinforced diaphragm 60. it is fastened to the flanges 48 ofthe beams that are closest to the adjacent rigid portions 34 as shown inparticular in FIG. 11. The shape and the fastening of the diaphragmsegment are the same as for the diaphragm segment of each rigid portion34.

The partition 20 is thus made up of the framework and of the diaphragmsegments 60 that it carries.

FIG. 9 shows how one of the rigid portions 34 is fastened to the primarystructure of the airplane. The bottom panel 26 extends under the floor76 of the airplane, in contact with the bottom face of the floor. Thefloor is cut out to provide an opening 78 in register with each beam 40.For each beam, a fitting 80 is rigidly fastened to the back of the panel26. A bottom end of the beam 40 has an extension 82 connected to thefitting 80 by conventional connection means using a pin and ball joints.On one of the beams of the rigid portion 34, this connection is suitablefor taking up forces in the three X, Y, and Z directions and fortransmitting movements along the same directions. On the other of thebeams the connection to the fitting is suitable for transmitting forcessolely along the X and Z directions.

At the level of the floor 76, sealing with each beam 40 is provided inthis example by means of a gasket having a shape like a note in musicnotation. The gasket 84 thus has a bottom portion 86 of circular profilethat is extended upwards from its rear face by a flank 88. The front andrear portions of this gasket are protected by two straps 90. The rearstrap is sandwiched between the gasket and the front face of the beam40, while the front strap 90 is S-shaped, matching the shape of thefront face of the gasket. The gasket 84 is thus protected from bruisingobjects that might be found on the floor. In order to protect it duringassembly and disassembly operations, it is advantageous for the gasketto be preassembled with its two straps before being put into place.

With reference to FIG. 7, the connection in the top portion between eachbeam 40 and the primary structure of the airplane in this example isprovided by means of a connecting bar 90. Each of the connecting bars 90extends essentially in the Z direction. The connecting bar 90 isconnected to the frame 14 in front and to the beam behind, the twoconnections being hinges about hinge axes 92 that are parallel to the Ydirection in the present example. Since the connecting bars extend inthe Z direction, they can transmit forces and movements in thisdirection only. Thus, provision is made for at least the top portion ofthe beam 40 to be capable of moving substantially relative to theprimary structure of the airplane. In each rigid portion 34, for any oneof the beams, the connecting bar 90 is of fixed length whereas theconnecting bar 90 associated with the other beam is of adjustablelength. Although this constitutes a statically undetermined assembly ofthe first degree, the geometrical inaccuracies of the assembly and theability for one of the connecting bars to be adjusted makes it possibleto accommodate that.

Sealing between the partition 20 and the parts fastened to the fuselage,at the top and on the sides is provided by a diaphragm 61 that isindependent from the diaphragm 60 but that is preferably made out of thesame material. The diaphragm 61 may itself be subjected to large amountsof movement, e.g. by plus or minus 20 mm in the general plane of thepartition in the Y and Z directions, and plus or minus 10 mm in the Xdirection. Thus, in FIG. 8, reference 61 a shows the nominalconfiguration of the diaphragm, reference 61 b shows its positionreversed along the X direction, reference 61 c shows its raised positionalong the Z direction, and finally reference 61 d shows a configurationwhich is both raised and reversed. As can be seen in FIG. 8, the edge ofthe top end of the diaphragm 61 is rigidly fastened to a locallyhorizontal panel 100 that is itself fastened beside its top face to theframes 14. This fastening is performed in this example by sandwichingthe diaphragm 61 between the panel and a strap 102. If the partition 20is removed, the diaphragm 61 may be left in place and may be deployedrearwards in a cylindrical configuration about the axis 6 in order toperform a lining function. It will then have the configuration 61 eshown in FIG. 8.

FIG. 14 shows how the diaphragm 60 is fastened at the bottom in sealedmanner to a rigid portion 34. The bottom ends of the beams 40 carry across-member 102 that presents a vertical plane bottom face 104 and amiddle plane face 106 that is parallel to the Y direction and thatslopes relative to the X direction, facing upwards a little. Thediaphragm 60 is sandwiched between this face and a strap 107 fastenedrigidly to the cross-member by suitable means that are not shown. Thebottom end edge of the diaphragm extends at a distance from the top edgeof the note-shaped gasket 84. Sealed fastening of the diaphragm at itstop portion is performed in analogous manner.

For the connections via a flexible portion, as shown in FIG. 15, it isthe rear strap 90 of the note-shaped gasket that presents the face 106and carries the diaphragm 60. At this location, the gasket merely comesto bear against a face connected to the fuselage.

The partition is installed by means of the following method.

All systems and cabin-lining trim are removed over a distance of about500 mm on either side of the partition that is to be installed. Thesystems and trim are put back into place after the structures have beeninstalled.

The rigid subassembly 22 that is to remain permanently is installedduring conversion work in which the airplane is unballasted as is thepractice for a major repair. While conserving the integrity of thelongitudinal stiffeners, sealing is established between the fuselage andthe subassembly in the manner described below. For this purpose, each ofthe stringer passages is sealed, as are the passages for varioussystems.

The removable portions 34 are installed.

Thereafter, the removable flexible portions 32 are installed.

Provision may be made to fasten the diaphragm segments 60 of the rigidportions 34 to said rigid portions before they are fitted to thefuselage.

Finally, sealing is completed by laying the various gaskets of thediaphragm 61 type or of the musical note type in the zones wheremovements are controlled.

With reference to FIG. 10, the side portion of the diaphragm 60 isconnected in sealed manner to the frame 14 by being sandwiched between arear face of the frame and a strap 112 that is held rigidly in positionagainst the frame by means of an assembly using bolts and captive nuts.

The frame is fastened to the skin 28 by means of its base 122, except inthe location where the frame extends across a stringer 116 such that thebase 122 goes round the stringer. The frame and the stringer aremutually perpendicular to each other at this location. They do notintersect and they are not locally coplanar. The junction on this sideof the frame between the frame 14 and the stringer 116 is sealed bymeans of a block 118 of sealing material that is molded in situ so asconnect the frame in sealed manner to the stringer and to the skinbeyond the stringer. This junction is made on portions of the frame andof the stringer that are spaced apart from their longitudinal ends.Specifically, the block 118 is made of an elastomer such as silicone.With reference to FIGS. 16 to 21, molding is performed by means of amold 124 comprising a plurality of portions 126 and 128.

The two portions 126 are solid, rigid, and in the form of plates. Theyare generally symmetrical to each other and are placed on either side ofthe plane of the web of the frame 14. Each of them presents a notch 130enabling it to be placed astride the stringer 116 and to be in contactvia its base 132 with the frame 14 and with the skin 28. Each of theseportions 126 makes sealed contact all along its surface making contactwith the frame, the skin, and the outside surface of the stringer. Byway of example, and with reference to FIG. 19, this sealing is achievedby means of a flexible O-ring 134 housed in a groove 136 in the base. Ina variant embodiment shown in FIG. 20, the base 132 has a series ofbaffles 138 following one another across the width of the base, withnone of these baffles receiving a gasket.

The portions 124 are made of a material that is selected to ensure thatit does not adhere to the injected elastomer. By way of example they maybe of made of polytetrafluoroethylene (PTFE) or of polyamide 1,1 that isknown as rilsan, for example.

Each of the portions 124 presents a cavity 140 into which the elastomeris injected and that serves in particular to receive the base 122 of theframe. Above this cavity, the portions 124 present respective faces 142whereby they make surface-to-surface contact with the corresponding faceof the frame 14. The two portions 124 are clamped against each other byclamping means such as self-blocking fasteners 144 and 146 that extendparallel to the stringer 116. One of these clamping means 146 may bedesigned to have a V-shaped configuration and pass between the frame 14and the stringer 116, under the frame while being in direct contacttherewith. These clamping means come to bear against the chamfered outerfaces 147 of the portions 124.

If the stringer 116 is of relatively simple shape, it may suffice toperform the molding by means of the two portions 126. Nevertheless, asshown in this example, the stringer may be of an S-shape, being open onone side. It is then preferable to use two other portions 128 for themold. Specifically, these portions are stoppers in the form of boneshaving a narrow portion in the middle. These stoppers are inserted in ahousing formed by the stringer, inside that housing, and they are heldby means of a clamp 143 clamping them perpendicularly to the web of thestringer. Each of the stoppers may project above the stringer, as shownin FIG. 21. The material from which the stoppers are made is selected sothat it does not adhere with the injected elastomer. By way of example,it is possible to use a polymer having closed cells.

In this example, use is also made of rigid cores or blocks 149 made ofelastomer that are polymerized prior to injecting the remainder of thematerial and that are installed directly in the housing in the stringer116 between its face 150 facing towards the skin and the skin itself.Specifically, two blocks 149 are used that are placed one above theother, one bearing against the skin and the other bearing against thisface of the stringer. They are installed in register with the web of theframe 14 prior to closing the mold. These blocks improve the overallrigidity of the molded gasket after it has solidified.

Injection is formed from only one of the portions 126, by means of aninjection hole 152 provided for this purpose, using an endpiece that isconnected to a tank of liquid elastomer. The two portions 126 areprovided with vent holes enabling the cavity to be filled completely.

The sealing block is made as follows.

The zone that is to receive the elastomer is cleaned.

The two portions 126 of the mold are put into place in front of andbehind the frame, together with their clamping means.

The two blocks 149 are installed.

The two stoppers 128 are put into place, compressing them initially byhand, as is made possible by the section of the stringer. Thereafterthey are clamped by means of the clamp.

The liquid elastomer is then injected. In the example of FIG. 20, duringinjection, one or more baffles becomes partially or completely filledwith the elastomer. In particular, the liquid comes into contact withthe blocks 149 that are embedded therein.

After the elastomer has polymerized, the two stoppers 128 are removedand then the plates 126 are removed by cutting through the self-blockingfasteners 144 and 146. Once the portions 126 have been removed, theself-blocking fasteners are cut once more flush with the faces (inparticular the face 147) of the solidified elastomer block 118 fromwhich they emerge. A segment of each fastener thus remains permanentlyinside the block.

The sealed joint made in this way does not hide any structuralfastening, so the connection between the frame and the skin remainsaccessible, as does the connection between the stringer and the skin,etc.

These operations are performed on a given frame for each of thestringers. The outside dimensions of the molded elastomer block 118 thatis installed at each stringer passage are identical for all of thestringers, with this applying even though the stringers may themselvesbe of different shapes and/or dimensions depending on the stringersegment under consideration. The same applies for the through holes(sometimes called mouse holes) constituting the space between the frameand the stringer in question, which space may present cutouts thatdiffer depending on the dimensions of the stringer and the direction inwhich the frame is put into place. The various segments of the frame mayalso be of different dimensions. The above-described mold can be used oneach occasion in spite of these differences in terms of dimensions andconfigurations, since the mold is designed to have dimensions that arelarge enough to enable it to be compatible with all such situations.

FIG. 23 is a force diagram showing the forces exerted on an intermediatebeam 40 by the diaphragm segments 60 that it carries. It is explainedbelow how the partition is made so that these forces are balanced whenthe two nearest beams 40 are not at equal distances from theintermediate beam.

In contrast, FIG. 22 shows the situation in which these forces are notbalanced.

Reference l₁ designates the distance as measured along the Y directionbetween the web of the intermediate beam 40 and the web of the beamsituated on the left and co-operating therewith to support the leftsegment 60. Similarly, reference l₂ designates the distance between thewebs of the beams 40 supporting the diaphragm segment situated on theright. It is assumed herein that the distances l₁ and l₂ are differentfrom each other, with the distance l₂ in this example being equal toabout 1.5 times the distance l₁.

The beam 40 in a main horizontal section thereof is subjected to a forceF₁ that is exerted by the diaphragm segment situated on its left and toa force F₂ that is exerted by the diaphragm segment situated on itsright. It is assumed here that these forces extend in a horizontalplane.

The angle θ₁ designates the angle of the force F₁ acting in a directionthat is tangential to the diaphragm at its edge, relative to the Ydirection, and the angle θ₂ designates the corresponding angle relatingto the force F₂. Under such circumstances, the two angles θ₁ and θ₂ areequal. This is because the front faces 50 of the flanges 48 also formrespective equal angles θ₁ and θ₂ relative to the Y direction, theflanges being symmetrical relative to each other about the plane of theweb of the beam 40.

Given the difference between these distances, the force F₂ is greaterthan the force F₁. Since these two forces act in directions that aresymmetrical about the plane of the web, they have a resultant R that isdirected towards the rear and that does not lie in the plane of the web,but that is directed towards the right. The beam 40 is therefore notloaded in balanced or symmetrical manner by the two segments 60. Thepoint of application of this resultant is the front end of thehorizontal section of the beam. It gives rise to a twisting moment aboutthe center of inertia 63 of the section, which center lies in the web ofthe beam halfway between its front and rear edges. There is thus anon-zero distance d between this center of inertia and the resultant R,such that the resultant generates a twisting moment about the center ofinertia. In such a situation, it is necessary for the beam to havesufficient material to enable it to withstand such a twisting moment,given that it must also be capable in conventional manner ofwithstanding a bending movement and a normal force.

In the situation of FIG. 23, the distances l₁ and l₂ are the same as inFIG. 22, but the angles θ₁ and θ₂ are different. The angles are selectedin such a manner that the resultant S of the forces F₁ and F₂ lies inthe plane of the web of the beam 40 and is thus parallel to the Xdirection. This result is obtained by selecting the angle of inclinationfor the front faces 50 of the flanges 48, which flanges are no longersymmetrical, in such a manner that they form respective angles θ₁ and θ₂with the Y direction such that:

θ₂=arctan(tan θ₁×l₁/l₂)

The faces 50 against which the diaphragm segments makesurface-to-surface contact have the same angles of inclination θ₁ and θ₂respectively relative to the Y direction. The shape and/or thedimensions of each segment is/are adapted so as to obtain this result.By way of example, it may be necessary to increase the radius ofcurvature of the right segment compared with the situation shown in FIG.22. This might result in an increase in the weight and the volume of thesegment, but that increase is not significant, and on the contrary isnegligible compared with the total weight saving achieved for thepartition as a whole by means of this arrangement. This ensures thatthere is no unwanted twisting resultant.

Thus, the shape of each diaphragm segment takes account of the realshape of how that segment is anchored on the beams, which itself takesaccount of the spacing between the beams. This serves to minimize theforces that the diaphragm segment 60 imparts on the primary structures.

On beams for which the distances l₁ and l₂ are equal, the angles θ₁ andθ₂ are equal.

Over the major fraction of its length, each diaphragm segment is formedby a single layer of silicone-impregnated poly-para-phenyleneterephthalamide. The diaphragm may weigh 0.5 kilograms per square meter(kg/m²). Selecting this material serves to minimize the weight of eachdiaphragm segment and makes it equivalent in terms of strength to adiaphragm made of aluminum alloy and having a thickness of 0.2 mm. Suchan aluminum alloy diaphragm is not available and is unsuitable forinstallation because of its fragility, which means that it needs to havea minimum thickness of 1 mm for fabrication reasons and to ensure it isrobust against human factors. A weight saving of about 500% is thusachieved compared with an equivalent diaphragm made of aluminum alloy.The diaphragm is nevertheless robust in spite of its low weight. Thediaphragm reversing in the event of a reversal of the pressuredifferential does not give rise to problems. The diaphragm segments 60withstand not only mere pressure and suction stresses, but can alsocoexist with the possible damage and wear of human origin.

As shown in FIG. 24, it is advantageous for the material of thediaphragm to be of double thickness where the diaphragm is sandwichedbetween the strap 64 and the flange 48, it being understood that this isa zone where the diaphragm is stressed particularly greatly. Thisdoubling of thickness can be achieved merely by folding the materialforming the diaphragm, and by placing a reinforcing element such as arod 67 in the fold so as to prevent the fold being flattened. The rod 67may for example have a diameter lying in the range 2 mm to 3 mm.Specifically it is made of a polyamide material. The rod extends at adistance from the zone of surface-to-surface contact between the strap64 and the flange 48 and it is not sandwiched between them.

The rod 67 may be placed in the mold that is used for impregnating theresin with the elastomer material. For this purpose, the impregnatedmaterial forming a single layer receives the rod and is folded around itbefore the elastomer is polymerized.

Facing the diaphragm segment 60, and on the same side as the center ofcurvature of the diaphragm, the strap 64 presents a face 69 ofcylindrical shape facing the diaphragm and having its own center ofcurvature situated on the side of the opposite face 69 of the diaphragm.In the event of the diaphragm being reversed, this face receives thediaphragm, which can bear thereagainst without running the risk oftearing.

The above-described partition 20 presents numerous advantages. It can beput into place and removed. Sealing is provided by means thataccommodate both the structural deformations that arise by virtue of theairplane being used and also any geometrical inaccuracies in the variousportions that need to be sealed, in particular if the airplane hasalready been fabricated. The combination of fixed and rigid portionsalso makes this possible. The number of fastenings that need to befastened and/or undone when installing the partition in the fuselage orwhen removing it is small.

By way of example, the time required for removing the partition may beless than 24 hours. The weight of the partition as a whole may forexample be about 800 kilograms (kg).

The partition preferably extends over the major fraction of thetransverse area of the inside volume of the fuselage.

As can be seen in FIG. 1, the partition 20, once in place, separates azone 109 situated in front of the partition from a zone 111 situatedbehind it. The zone 109 may be subjected to cabin pressure, unlike thezone 111. Or else the zone 111 may contain a liquid such as fuel, unlikethe zone 109.

Provision may be made for the top panel 24 to be stabilized by means ofa plurality of fittings connecting it to the skin 28, these fittingsextending for example along four consecutive frames. Provision may bemade for the bottom panel 26 to be stabilized in the same manner. Therigid subassembly 22 may also have two special gasket-carrying sectionmembers installed on the left and the right of the frame.

Naturally, numerous modifications may be made to the invention withoutgoing beyond the ambit thereof.

The method of making the block 118 may be implemented on parts otherthan frames and stringers, and on parts other than of a fuselage, forexample on a rib part of an aircraft wing.

1. A method of making a sealed junction between elongate aircraft partsthat extend locally in main directions that are not mutually parallelwherein, the following steps are performed: assembling a plurality ofportions of a mold on the parts; and injecting a sealing material intothe mold.
 2. A method according to claim 1, wherein the parts form aframe and a stringer of a fuselage.
 3. A method according to claim 1,wherein, prior to injection, at least one block of sealing material isinstalled in the mold.
 4. A method according to claim 1, wherein atleast two of the mold portions present respective notches for receivingone of the parts.
 5. A method according to claim 1, wherein at least twomold portions are clamped one towards the other by using clamping meanssuch as self-blocking fasteners, and then after injection the clampingmeans are cut off level with a face of the sealing material.
 6. A methodaccording to claim 1, wherein at least one of the mold portions isinserted in a housing facing a face of one of the parts that is orientedin a direction opposite to the other part.
 7. A method according toclaim 6, wherein the or each inserted mold portion is made of a cellulardeformable material.
 8. A method according to claim 1, wherein a sealedjunction is made using the same mold portions on other parts of the sameaircraft presenting shapes and/or dimensions that are different from theshapes and/or dimensions of the parts.
 9. An aircraft, comprisingelongate parts that extend locally in main directions that are notmutually parallel, and a molded block forming a sealed junction betweenthe parts.
 10. An aircraft according to claim 9, the aircraft includinga structural portion such as a fuselage, a wing, or a tail, thestructural portion comprising: a wall separating the inside from theoutside of the structural portion and comprising fractions that definebetween them an inside volume of the structural portion; and astructural partition separating zones of the volume from each other, thepartition comprising a flexible diaphragm suitable for deforming andsupports supporting the diaphragm in discontinuous manner; the blockproviding a sealed junction between the partition and the remainder ofthe structural portion.